//if ABC is disabled (see in setup function) sensor should be calibrated manually. leave outdoors (=400ppm) with no direct sunlight for >20min, then connect HD pin to GND for at least 7 seconds.
while(!mhz19.disableABC()&&mhz19abctries>0){//disable automatic baseline correction (abc does calibration every 24h -> needs to have 400ppm co2 level sometime during that time)
delay(500);//wait some time for mhz to be initialized